Hinata Kato on N7, the Sports Bra Built to Stop Breasts From Moving

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Overview

In this video, Hinata Kato of HINA Channel announces the restock of N7, the sports bra they developed themselves. The first run of 10,000 units sold out immediately when it launched about two years earlier. Kato says the relaunched version was redesigned and upgraded using two years of customer feedback. The video covers why they made a high-support bra, how long it took, what changed in the new version, how to wear and care for it, and who should not buy it. Kato's central position is that, for anyone trying to keep or improve their bust, preventing breast movement during exercise matters more than anything else.

14 min read
0:54

What N7 is meant to do

Kato describes N7 as a sports bra that provides high support and protects the Cooper's ligaments. In the video they tighten the laces and show their upper chest during movement, saying the breasts stay put once the laces are tightened. Their reasoning is that even very light exercise makes breasts move in three directions, and that this movement gradually stretches the Cooper's ligaments and leads to sagging. For that reason, Kato argues, a sports bra matters for three groups: people trying to increase their bust size, people who want to avoid sagging, and people still growing who feel pain when their breasts bounce. The product was designed with activities like jumping rope, running, and HIIT in mind.

Kato also explains the problem they set out to solve. Bodies differ, so a high-support bra sized for a C cup will still let an A cup move. In their view, no sports bra on the market fits each individual perfectly. That is the gap N7 is meant to fill: a bra whose fit can be adjusted to the person wearing it.

2:38

The origin story: jumping rope and a burn

Kato explains the product's background through their own experience. They say they used to weigh 20 kg more than they do now, at a time when they had goals such as auditioning for Morning Musume. Their main aerobic exercise then was jumping rope, which they call the only full-body exercise on land and an effective way to lose fat across the whole body. They jumped rope every day.

Their breasts bounced a lot when they did. Kato was between a B and a C cup at the time, closer to a B, and wanted to increase their bust size. In their view, breasts that sag and bounce don't make for a good bust. To stop the movement, they wore a sports bra over an underwired bra. That worked at first, but sweat caused friction, the fabric wore thin, and the wire eventually poked out. The wire rubbed against their skin over and over and caused a severe burn that oozed and was very painful. Kato shows the scar on camera with a warning to viewers, says it is still visible, and says they hate it. They describe the experience as feeling that all their effort to look beautiful had been wasted, and call it a very depressing period. They then went looking for a sports bra that would truly stop movement and concluded that none existed.

4:52

Four years of development without the vocabulary

Kato says they funded the bra with money saved since starting YouTube. They show a photo posted in 2018, when development began, and say the project took four years in total. The first prototype they wore is described as looking like a loincloth.

The hardest part, they say, was communication. They didn't know the technical terms that textile professionals use, so they started drawing illustrations to explain what they wanted. One concept was modeled on a corset, partly because corsets can be adjusted across many sizes. Kato says they kept talking with the staff and redid many things over and over until N7 was finished. They say the product is made with care from the fabric to the finish, and they become emotional on camera talking about it.

The first release and the criticism behind the update

Kato thanks viewers for the reviews of the first version. They say their core principle is that selling something has to benefit both sides, and that this should never change. They wanted to make something people would be grateful for, because it would have helped them. They founded a bust-focused brand, and N7 was its first product.

Kato also acknowledges that not all the reviews were positive. They quote three complaints: the bra was very hard to put on because of its high support, it rubbed and hurt the armpits, and it came in only one size, which made it hard to wear. They say these opinions shaped the upgrade.

6:57

Design choices: straps, back, and under-band

Kato then goes through the design decisions they care most about. The shoulder straps are thick because thin straps strain the shoulders. They add a reason tied to bust care: in their view, restricted blood flow keeps nutrients from reaching the bust and works against breast enhancement, so they avoided anything that cuts off circulation. The strap material is soft so it doesn't put too much strain on the body, and the thick straps are also meant to lift the breasts.

The back has a leaf-shaped cutout. Kato says it is mostly open so sweat doesn't build up and the wearer doesn't overheat, while the straps and front still provide the support. It is made of a quick-drying power net. They also say the cut looks stylish and makes the spine line look good.

Under the bust, the band is thicker to support the ribs. Kato says the ribs shouldn't be squeezed too tightly, and that good posture helps keep the bust in a nice position, so they chose a band that tightens only lightly.

Laces that are actually shoelaces

The front laces, which Kato calls ribbons, are how each wearer adjusts the fit to their own bust. Kato reveals that they are actually shoelaces. They chose shoelaces because they rarely break, stretch well, and look stylish. The laces can be tied loosely or pulled firmly for high support. Kato also mentions that tension can be adjusted by folding the lace in half.

Each bra comes with two laces. The black bra comes with black and grey laces, and the white bra with beige and brown. Kato says the colors were chosen after many discussions with a color coordinator. They encourage buyers to swap laces and even say regular shoelaces can be used instead.

9:30

Pads, tags, and the white color

The bust pads combine fabric with thick padding to support the bust. Kato says they are made at a factory with a long history of making bust products, and because the pads can only be ordered from that factory, production is very slow.

The tag was changed to the kind used by high-end brands. Kato says they wanted people to feel motivated by how the bra looks, not just by its support. The white version is described as an off-white, closer to beige, chosen to match Japanese skin tones. Kato says they read all their direct messages and quotes buyers who said the white one was cuter than in the website photos. Some people who bought both said the black looks cool and the white looks cute. Later in the video, Kato shows themself wearing the white version because viewers asked to see it.

10:50

What actually changed in the renewal

Kato then lists the specific updates.

  1. Thicker bust pads. The pads are slightly thicker so they last longer for people who wear and wash the bra often, and so they give even more support. Kato says that if you jump rope in it, it feels like you're holding your breasts in place with your hands. They mention that the body fat around the area still jiggles, but the breasts themselves are held. Using a visual comparison, they say the Cooper's ligaments act like rubber bands that support the chest, stretch with movement, and are said to be hard to return to their original shape once stretched, like a hair tie. They claim N7's support keeps them from stretching and contracting.
  2. Lower armpit fabric. The bra is assembled from separate panels, and the fabric differs from part to part. Because some people had chafing and pain under the arms, the fabric there was lowered. Kato says the bra keeps a high-sided design for support, so side and underarm fat can still be gathered in.
  3. Printing. The back line and the inside are now printed with a print that Kato says resists sweat and washing.
  4. The tag. It was redesigned to the high-end style described earlier, meant to make wearers feel more confident.

The box was also redesigned. Kato says they tried several sizes and picked the one they thought was best. The packaging includes English text explaining the intent behind the product, because they expect some buyers won't know who Kato is. The goal, they say, is for N7 to feel like a treasure the moment it arrives.

Why the website explains the "why"

Kato also redesigned the N7 website, and they explain why with a general point about motivation. Whether in dieting or anything else, they argue, doing something while understanding its purpose changes how fast you see results. Their example is glute training: its effectiveness is completely different depending on whether you understand what it's for. Understanding the meaning raises motivation and makes it easier to keep going. On the same logic, the site now explains why protecting the Cooper's ligaments matters. Kato adds that if you're working to increase your bust size, the best approach is to protect your breasts from movement while exercising, based on their own years of trying.

14:52

How to put it on correctly

Because the bra is high-support, Kato recommends putting it on over the head rather than stepping into it. For most people the pelvis is wider than the shoulders, so pulling it up from the legs could tear it. The shoulders are flexible enough to work it over the head.

They demonstrate the steps:

  • Put your arms through the bra.
  • Bring your chest together toward the center.
  • Tighten the laces, starting from the bottom for maximum support. Kato says this pulls the chest up and hides cleavage.
  • Tie the laces in a bow.
  • Pull the bottom band down while tucking in the side fat, then do the same on the other side.

Kato says this puts the bust in the right position and keeps it from bouncing.

16:15

Washing and how long it lasts

Kato says they're being candid here. They wear N7 every day and wash it in a laundry net in the washing machine and dryer. Under that routine, they say, the high support stays like new for about a year. After a year it is still usable, even with machine washing and drying. However, machine washing twists some parts, including the elastic. If you want to be careful, they suggest hand washing. The bra is designed to dry quickly, so they recommend drying it with a bathroom dryer. Kato also recommends a specific detergent: you dissolve the powder in water and soak underwear in it for five minutes. They say the thicker pads were partly meant to keep support up for machine washing, and that with good care the bra should stay perfectly wearable.

17:39

Use outside of workouts, and whether compression is a problem

Asked whether N7 can be worn for things other than exercise, Kato says yes, including yoga and strength training, the same as a regular sports bra. For daily life at work, school, or a part-time job, they recommend wearing an underwired bra or shaping underwear to help shape the breasts. They suggest N7 for physical education classes or physically demanding jobs such as delivery work, where a regular bra can't support certain movements.

Kato says they've been asked twice whether it's okay that the bra compresses the chest. They say that because it is high-support, it does compress and gives a held-in feeling. The upper part is power net, designed to keep its shape and stay full on top rather than flattening the chest, while the lower part of the breast is pressed down. Their honest view is that they worry about breast movement more than anything else. They stress this is a personal opinion, since they built N7 for their own use. They say they do body work to increase their bust size and that compression hasn't been a problem, because N7 gave them breasts they're happy with. They add that they're afraid to use ordinary sports bras given how hard they work on their bust, and they present themself as proof.

19:45

Sizing, and who should not buy it

Kato is unusually firm on sizing. They recommend N7 for people who wear A to E cups in regular bras with an underbust of 62.5 cm to 77.5 cm. For reference, Kato's own underbust is 70–75 cm, they're an E cup, and they wear E and F bras.

Because bone structure differs, they tell E cups with an underbust over 75 cm not to buy N7, and repeat that anyone outside the range should not buy it, even if they think they could make it work. Their reasoning: forcing yourself into a bra that's too tight pushes side fat out and causes chafing, and people with larger breasts will spill over the top. Just as you shouldn't wear the wrong bra size, they say, you shouldn't wear the wrong sports bra size. N7 is high-support and should be treated as a completely different product from a regular sports bra. Kato adds that they themselves found N7 hard to wear after gaining 6 kg.

Kato says larger sizes, also high-support, are in development. Only the design and sizing remain to be finalized. They estimate release at the end of the year at the earliest and January at the latest, and ask anyone who isn't, in their words, a slim E cup with a 75 underbust to wait rather than force themselves into the current size.

22:05

What comes next

Kato closes by describing N7 as a bust-protection brand that wants to keep making helpful products. Their next projects are a night bra and shaping underwear, which they're developing from their own breast-enhancement experience. They say the work is very hard, that they started over and are making them now, and that they might not succeed. Kato adds that the N7 Instagram account, not the HINA Channel account, will be first to announce plus sizes, underwear, and the night bra, and suggests that people who keep missing restocks follow it. Kato says they hope N7 will let people enjoy exercise every day without stress.